package demo_JUC.PandC;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 线程之间的通信问题：生产者和消费者问题！
 * -- 等待唤醒，通知唤醒
 * 线程交替执行 A B 操作同一变量
 * A num+1
 * B num-1
 */
public class demoJUC {
    public static void main(String[] args) throws InterruptedException {
        Data data = new Data();

        new Thread(()->{for (int i = 1; i < 50 ; i++){
            try {
                data.increment();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }}, "A").start();
        new Thread(()->{for (int i = 1; i < 50 ; i++){
            try {
                data.decrement();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }}, "B").start();
        new Thread(()->{for (int i = 1; i < 50 ; i++){
            try {
                data.increment();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }}, "C").start();
        new Thread(()->{for (int i = 1; i < 50 ; i++){
            try {
                data.decrement();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }}, "D").start();
    }
}

// 等待，处理，通知
class DataJUC{
    private int number = 0;
    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition(); // 锁的监视器

    public void increment() throws InterruptedException {
        lock.lock(); // 加锁
        try {
            // 业务代码
            while (number != 0){
                // 等待
                condition.await();
            }
            number++;
            System.out.println(Thread.currentThread().getName() + "=>" + number);
            condition.signalAll();
        } finally {
            lock.unlock();
        }
    }
    public  void decrement() throws InterruptedException {
        lock.lock(); // 加锁
        try {
            // 业务代码
            while (number == 0){
                // 等待
                condition.await();
            }
            number--;
            System.out.println(Thread.currentThread().getName() + "=>" + number);
            condition.signalAll();
        } finally {
            lock.unlock();
        }
    }
}